WOMEN voters are crucial to the outcome of any British general election. That might sound like a statement of the obvious, and you only have to replace the word 'women' with 'men' to see how ridiculous it can be.

Nevertheless, it's true that, if women did not vote, Labour would have won every election since 1945. That gives more of an indication as to why politicians tend to get into a lather about the semi-mythical 'female vote' and why pollsters are so keen to identify any changes and trends at an early stage.

The latest data is a boost to David Cameron's attempts to modernise his party. By talking less about immigration, crime and the EU and more about family- friendly working and the environment, it seems he has attracted back some of the female voters that were wooed by Tony Blair back in 1997.

Curiously enough female voters have always tended to back the Tories rather than Labour, bucking the trend seen in other European countries. Mr Blair broke the trend, but polls this year have suggested that it may turn out to have been a blip.

Britain may be closer to the US model, where working mothers - the so-called 'soccer moms' - are a key constituency and formed the backbone of Bill Clinton's coalition of support.

A recent Populus poll showed that a big gender gap has emerged, with the Tories doing much better among women than men. Previous polls only given the Tories a smaller lead.

Overall, the Tories are only a little ahead of Labour; a Populus poll earlier this month put them on 34%, one ahead of the Government. The Liberal Democrats were on 19%.

But analysis of data collected since the party conference season show the two bigger parties are level on 34% among men - so the Tories' lead comes entirely from women, who favour them this month by 37 to 31%.

The gender gap is even larger when voters are asked how they would vote in three or four years if Labour were led by Gordon Brown - which seems a near-certainty - and the Tories by Mr Cameron.

The Tories' overall lead has narrowed from 42 to 34% against a Brown-led Labour Party last month from 38 to 34% now.

Men favour Labour under Mr Brown by 37 to 34% over the Tories under Mr Cameron, but the position is more than reversed for women. Women voters prefer the Tories by 42 to 30%.

These trends contrast sharply with most of the Blair era, when the historic gender gap favouring the Conservatives virtually disappeared.

The statistics spell bad news for Mr Brown, and have Labour strategists scratching their heads. They believe the party has done much to improve the lot of working women with increased maternity provision, more nursery places and more childcare provision, as well as the minimum wage, which benefits low-paid, part-time working women more than anyone else.

Shadow Welsh Secretary Cheryl Gillan thinks the Cameron factor has had an impact.

'You can identify with him more readily, he doesn't live on another planet,' she says. 'He is trying not to pontificate, he is not without problems in his family life, he is concerned about the future and a lot of women will identify with that.'

The new Tory leader is 'less brutal, more moderate' than some other senior politicians, she adds, another factor that counts in his favour. 'There is a lack of hysteria about David which women like. Women are the ones who pick up the children when they fall over, they are often the anchor of a family; I think they see that lack of hysteria in him, too.' But policies are critical too. 'He knows what concerns people, and what really concerns people is how are we going to make sure there is a future for the environment, how are we going to educate our children and look after our older relatives?

'I think he's the first politician for a long time to try to move the debate on to something different.'

So is it still worth dividing the electorate up into men and women? Is it actually useful for politicians or for the voters themselves?

'You've always got to have a breakdown of your audience, and the simplest breakdown is by sex. It's still a useful business tool,' says Ms Gillan.

'I'm not sure the idea is old hat, quite the opposite when you look at the statistics. I think if you're preparing for a role in Government you need to cover the whole audience you need to address, so I think looking at women as a voting group does have relevance.' Liberal Democrat MP for Cardiff Central Jenny Willott isn't so sure. 'To assume that all women vote the same way is completely outdated, it's just not true,' she says. 'But I do think that women have a different approach to politics than men; while they might not vote the same way, they tend to look at issues differently from men.'

Not only do they think differently, they take longer to mull over the issues. No wonder politicians target them so assiduously.

'They also tend to make up their minds much later in election campaigns, and think much more carefully about the particular issues and arguments,' says Ms Willott.

'Men are much more likely to have made up their minds at an early stage in life and stick to it.'

So is British politics getting more in tune with what could loosely be termed women's issues?

'I think things have changed significantly, but that's not just down to politics. Issues like childcare are discussed in public in a way which they wouldn't have been 15 years ago - and they're issues that are becoming much more important to men too, and more and more MPs are affected by childcare issues.'

The 2005 general election saw family issues placed near the centre of the campaign for the first time. Next time they'll be even higher up, and whoever can control this agenda will have one foot inside Number 10.